//Tue Mar  8 12:32:42 CST 2011
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>

using namespace std;

class SimpleGuess
{
public:

    int getMaximum(vector <int> hints)
    {
        int sz = hints.size();
        int ret = 0;
        for (int i = 0; i < sz; i++)
        {
            for (int j = i + 1; j < sz; j++)
            {
                if ((hints[i] + hints[j]) % 2 == 0)
                {
                    if (hints[i] > hints[j])
                        ret = (hints[i] * hints[i] - hints[j] * hints[j]) / 4 > ret ? (hints[i] * hints[i] - hints[j] * hints[j]) / 4 : ret;
                    else
                        ret = (hints[j] * hints[j] - hints[i] * hints[i]) / 4 > ret ? (hints[j] * hints[j] - hints[i] * hints[i]) / 4 : ret;
                }
            }
        }
        return ret;
    }
};
